[Pontiac]

They still don’t know what penicillin really is. I mean it is a mold, but what sort? It has never been found in the wild. It wafted in though an open window and was ‘discovered’ but they have never isolated it in the wild. Ever bit of penicillin we have came from that one wayward spore.

Not to prove you wrong but you made me curious so I looked it up. According to Kenyon.edu the original Penicillium strain is no longer used. But another site I looked at did say that the original strain was rare.

One of the things Penicillium is most famous for is the drug penicillin. It was used to create the first antibiotic. The originial strain, Penicillium notatum, was discovered in 1920 by Sir Alexander Fleming. However, it was replaced with Penicillium chrysogenum, a more productive species, which is now the species used in manufacturing penicillin.

[TalonDJ]

Interesting. Thanks.

[VanShuyten]

Both notatum and chrysogenum are far from rare, unless you mean by comparison with other Penicillium species, or with molds in general that produce penicillin.

If you leave some moist bread out for a few warm days, there’s a very good chance that one of the blue mold colonies makes penicillin. The two species you mention are the two that make useable quantities of the drug.

The government did a little genetic engineering on the original chrysogenum strain by X-raying it to produce mutations and then selecting the resulting mutants for penicillin production.